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NESHAP Halogenated Solvent Cleaning—
May 2007
Revisions

Background
On May 3, 2007, EPA published revised air emission standards for hazardous air
pollutants from halogenated solvent cleaning operations that establish a facility-wide
annual emissions limit of 60,000 kg/yr of methylene chloride (MC), perchloroethylene
(PCE), and trichloroethylene (TCE), on a â€œrisk-adjustedâ€� basis. This was

Figure 1. Modern Vapor Degreaser

the first significant change in these rules since the National Emission Standard
for Hazardous Air Pollutants (NESHAP) for solvent cleaning operations was published
in 1994. The revisions mostly affect facilities with very big degreasers or a
large number of smaller units. Aerospace and military depots are exempt from
the new rule (due mainly to cost effectiveness and labor skill issues). All facilities,
including the general finishing industry, aerospace facilities and military depots
must continue to comply with the 1994 requirements.

The 1994 NESHAP covers vapor degreasing (Figure 1) and immersion (cold) cleaning.
Companies operating existing equipment, had until December 1997 (36 months)
to comply with the requirements. Cleaning machines that began operations after
November 29, 1993, (proposed regulation date) are required to comply with the
standards immediately after startup. In developing the standards, EPA focused
on equipment and work practices to achieve a level of control between 50 and
70 percent.

In 1994, the use of halogenated solvent cleaning by the metal finishing industry
was a common practice, although a declining use trend was already underway
due mainly to scheduled phase-out of certain solvents (e.g., Montreal Protocol
caused a production phase-out of TCA) and concerns over the NESHAP and possible
future regulations. Once the 1994 NESHAP was in place, there was an immediate
and major reduction in use of solvent cleaning over the next three years, followed
by a less steep, but steady decline. Figure 2 shows data from the Metal Finishing
Strategic Goals Program. These values are for quantities of solvent released
to the air on a sales normalized basis. The SGP started collecting data in
1997, although most companies also submitted data for 1994, which served as
a baseline. SGP data are still collected by the NMFRC, however there was insufficient
data to look reliably past 2005.

Today, solvent cleaning is still used by the aerospace industry, military
depots, precision cleaning operations, and to a lesser extent by the general
finishing industry. Most of these facilities use new solvents that are designed
for environmental compliance. The cleaning/degreasing equipment has also changed
significantly, it is often downsized and much more efficient and less polluting
(e.g., totally enclosed systems, carbon adsorption capture devices).

Regulatory Revision
Under the 1994 NESHAP, companies are required to meet emissions standards for
specific solvents and individual cleaning/degreasing machines. These rules
are still in effect. Under the revised rule:

EPA has established a risk-adjusted value for MC, TCE and PCE solvents,
based on their probability to cause cancer, and

emissions of these solvents from the total site must be below 60,000 lb/yr
on a risk adjusted basis.

Here is an example of a risk equivalent calculation. If a facility uses 4,000
lbs/yr of each of the above solvents, the risk-adjusted quantity would be:

MC:
4,000 lb/yr x 1.0 =

4,000
lb/yr

TCE:
4,000 lb/yr x 4.25 =

17,000
lb/yr

PCE:
4,000 lb/yr x 12.5 =

50,000
lb/yr

Total

71,000
lb/yr

There are no other additional equipment monitoring or work practice requirements
associated with the facility-wide annual emissions limit. Annual emissions of
PCE, TCE, and MC are determined based on records of the amounts and dates of
the solvents added to cleaning machines during the year, the amounts and dates
of solvents removed from cleaning machines during the year, and the amounts and
dates of the solvents removed from cleaning machines in solid waste. Records
of the calculation sheets showing how the annual emissions were determined must
be maintained.